The National Institute on Deafness and Other Communication Disorders, as the major Federal funding agency of research in communication disorders, wishes to take the lead in beginning to fill the persistent, long-standing need for epidemiologic data, and has identified the population of preschool Specific Language Impairment (SLI) children as a starting place for such studies. The purpose of this research will be to obtain prevalence data on SLI, in particular to: 1) Determine the prevalence of SLI in five-year-old children within urban, suburban, and rural environments within the United States; 2) Within each of the three environments, ascertain the percentage of SLI with primarily expressive language deficits, primarily receptive language deficits, those with both receptive and expressive deficits, and those with a concomitant phonological disorder; 3) Within each of the three environments, ascertain sex differences in the occurrence of SLI; 4) Within each of the three environments, identify possible risk factors associated with the occurrence of SLI; and 5)Within each of the three environments, identify the percentage of SLI children who have received or are receiving intervention for their communication disorder.